The present invention relates to a scintillation camera system adapted to emission computed tomography and designed to form an image of a particular area of a patient, and more particularly to a device for supporting the detector used in the system to detect the gamma rays emitted from the patient.
A scintillation camera system has a detector. The detector detects the gamma rays emitted from a patient. The energy of the gamma rays is converted into electrical signals. These electrical signals are supplied to a computer. The computer processes the signals, thereby reconstructing an image of a specified area of the patient.
In the scintillation camera system, a patient lies on a horizontal bed. Scintillation camera systems can be classified into two types. In the first type, the detector is located above the patient. In the second type, the detector is moved around the patient. The system of the first type is adapted mainly to form an image of a particular area of the patient. In this system, the detector is supported at the distal end of an arm, the proximal end of which is pivotally coupled to a stanchion provided beside the patient. The system of the second type is adapted mainly to emission computed tomography. In the system of the second type, the detector is supported at the distal end of an arm, the proximal end of which is pivotally connected to a rotary mechanism which can rotate about the axis of the patient.
In either type of scintillation camera system, the arm is rotated about its proximal end in order to adjust the position of the detector, with respect to the patient. More specifically, the arm is rotated to move the detector vertically. It is desirable that the detector is moved with its gamma ray-receiving surface positioned horizontally and opposing the patient lying on the horizontal bed. To this end, the arm comprises two cranks forming a parallel crank mechanism. Whenever the cranks are rotated, they remain parallel to each other. The detector is, therefore, also moved in parallel to the stanchion (or, to the rotary mechanism). The detector can thereby move in the vertical direction, while the gamma ray-receiving surface remains in a horizontal plane.
After the detector has been set in a predetermined position, it must be tilted by a prescribed angle, in some cases, in order to photograph, for example, the patient's head. U.S. Pat. No. 4,459,485 discloses a device which can incline a detector. This device comprises two cranks forming a parallel crank mechanism, and an auxiliary member having a two-forked distal end. The cranks support the proximal end of the auxiliary member at their respective distal ends. The detector is loosely clamped between the two prongs of the forked distal end of the auxiliary member. The auxiliary member is moved in parallel to a stanchion (or a rotary mechanism) of the type described above. Hence, the detector can move vertically, while its gamma ray-receiving surface remains in a horizontal plane. Further, the detector, which is loosely clamped between the prongs of the auxiliary member, can be tilted when required, whereby the gamma ray-receiving surface can be inclined to the horizontal plane. Even if the gamma ray-receiving surface is tilted by a prescribed angle, the detector can be moved in the vertical direction. As a result, this prior art device can facilitate the positional adjustment of the detector with respect to the patient.
However, since the forked distal end portion of the auxiliary member covers almost half the detector, it is considerably massive and heavy. When the prior art device is incorporated in a scintillation camera system, the system will inevitably be massive and heavy. Consequently, it is difficult to transport and install the scintillation camera system, and also the device supporting the detector must be large.